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A two-dimensional steady-state model is developed, in which, even though ion inertia is retained, a variable separation allows us to analyse separately the axial and the radial transports. For the axial transport (along magnetic field lines) an integral dispersion relation is derived that includes a nonlinear form that is obtained from the ion-neutral collision operator. The dispersion relation is solved for various values of the Paschen parameter, and the electron temperature and the axial profiles of the plasma density and plasma potential are calculated. The solutions of the dispersion relation are shown to have three asymptotic limits: collisionless, linear diffusion and nonlinear diffusion. For the radial transport, the rate of which is determined by electron cross-field diffusion, the full equations are numerically solved. The calculations are compared to probe measurements performed at various locations inside our helicon source for various magnetic field intensities and wave powers. The proposition that the measured increase in the plasma density with the increase of the magnetic field intensity is a result of an improved confinement, is examined. For the parameters of the experiment described here, this proposition implies that the electron collisionality is much larger than expected from electron-ion and electron-neutral collisions. A different explanation for the dependence of the density on the magnetic field intensity is suggested, that the density increase that follows an increase of the magnetic field intensity results from an improved wave-plasma coupling via the helicon interaction, causing a larger fraction of the total wave power to be deposited inside the helicon source.

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The Hall current plasma thruster accelerates a plasma jet by an axial electric field and an applied radial magnetic field in an annular ceramic channel. A relatively large current density (>0.1 A/cm2) can be obtained as the acceleration mechanism is not limited by space charge effects. Such a device can be used as a small rocket engine on board spacecraft with the advantage of a large jet velocity compared to conventional rocket engines (10000–30000 m/s versus 2000–4800 m/s). An experimental Hall thruster was constructed and operated in a broad range of operating conditions and under various configuration variations. Electrical, magnetic and plasma diagnostics, and as well accurate thrust and gas flow rate measurements, have been used to investigate the dependence of thruster behavior on the applied voltage, gas flow rate, magnetic field, channel geometry and wall material. The studies conducted so far have demonstrated a significant effect of channel material on thruster electrical characteristics and the existence of an optimal channel length for a given flow rate. Representative results highlighting these findings are presented.